A level control system of this kind is, for example, disclosed in U.S. Pat. No. 6,685,174. This level control system makes it possible to maintain the vehicle body of a motor vehicle at normal level. For this purpose, pressurized air is transferred from the pressurized air store into the air springs of the level control system in order to raise the vehicle body of the motor vehicle or pressurized air is transferred from the air springs via the compressor into the pressurized air store to lower the vehicle body when the vehicle body is no longer at the pregiven normal level. The storage pressure of the pressurized air store must lie within a specific range when the vehicle body is at the pregiven normal level in order to make possible, on the one hand, a rapid lifting of the vehicle body and, on the other hand, a rapid lowering of the vehicle body. If the storage pressure in the pressurized air store is too high, then a rapid lifting of the vehicle is possible but a rapid lowering of the vehicle body is not because, in this case, the pressurized air must be transferred from the air springs against the high storage pressure in the pressurized air store. The same applies when the storage pressure in the pressurized air store is too low which makes possible a rapid lowering of the vehicle body but not a rapid raising thereof.
The storage pressure of the pressurized air store varies because of different loading conditions and different level settings, which are inputted by the driver or by the control of the level control system (for example, in order to provide greater road clearance in an off-road vehicle). This can lead to the condition that the storage pressure lies outside of the desired range because of the instantaneous loading state and/or the instantaneous level setting of the vehicle body even though the storage pressure would lie within this range if the vehicle body would be disposed in the pregiven normal state. If the storage pressure is determined at such a time point, then this would lead to a filling of the pressurized air store with air from the atmosphere or lead to a discharge of the pressurized air store into the atmosphere even though this should not actually occur. Rather, only leakage losses or storage pressure fluctuations should be compensated in the pressurized air store via filling or discharge. The leakage losses and storage pressure fluctuations arise because of intense temperature fluctuations. One could solve the problem in that the storage pressure is only determined when the vehicle body is at the normal level but this often does not occur over a long time span.